METHOD AND CONVEYING DEVICE

Abstract

A method for supplying a consumer with a cryogen from a storage vessel, with the following steps: a) introducing part of the cryogen from the storage vessel into a volume that can be closed off, b) closing off the volume by first closing a supply valve arranged between the volume and the consumer, and then closing an inlet valve arranged between the storage vessel and the volume, c) vaporizing the cryogen in the volume so as to subject the volume to a pressure which is higher than a pressure prevailing in the storage vessel, and d) discharging the vaporized cryogen from the volume to the consumer when the consumer has a load requirement by opening the supply valve, wherein, when the supply valve is open, the inlet valve is opened as soon as the pressure in the volume falls below the pressure prevailing in the storage vessel.

Claims

1. A method for supplying a consumer with a cryogen from a storage vessel, with the following steps: a) introducing part of the cryogen from the storage vessel into a volume that can be closed off from the consumer and from the storage vessel; b) closing off the volume from the consumer and from the storage vessel by first closing a supply valve arranged between the volume and the consumer, and then closing an inlet valve arranged between the storage vessel and the volume; c) vaporizing the cryogen in the volume so as to subject the volume to a pressure which is higher than a pressure prevailing in the storage vessel; and, d) discharging the vaporized cryogen from the volume to the consumer when the consumer has a load requirement by opening the supply valve, wherein, when the supply valve is open, the inlet valve is opened as soon as the pressure in the volume falls below the pressure prevailing in the storage vessel.

2. The method according to claim 1, wherein during step d), the pressure prevailing in the volume is reduced to a supply pressure suitable for the consumer when the cryogen is discharged from the volume with the aid of the supply valve.

3. The method according to claim 2, wherein the supply pressure suitable for the consumer is less than the pressure prevailing in the storage vessel.

4. The method according to claim 2, wherein during step d), the supply valve is opened depending on the load requirement of the consumer.

5. The method according to claim 2, wherein during step d), the supply valve is controlled with the aid of an open-loop and closed-loop control device based on sensor signals from a pressure sensor arranged downstream from the supply valve and/or sensor signals from a flow sensor.

6. The method according to claim 1, wherein the inlet valve is closed as long as the pressure in the volume is greater than the pressure prevailing in the storage vessel.

7. The method according to claim 1, wherein heat is introduced into the cryogen during step c) with the aid of a vaporizer unit in order to vaporize it.

8. A conveyor device for supplying a consumer with a cryogen from a storage vessel, comprising: an inlet valve which is arranged between the storage vessel and the volume; supply valve which is arranged between the volume and the consumer; a volume which can be closed off from the consumer and from the storage vessel; a vaporizer unit; and, an open-loop and closed-loop control device; wherein the open-loop and closed-loop control device is configured to control the inlet valve in such a way that the inlet valve introduces a part of the cryogen from the storage vessel into the volume; wherein the open-loop and closed-loop control device is configured to control the inlet valve and the supply valve in such a way that the inlet valve and the supply valve close off the volume from the consumer and from the storage vessel; wherein the open-loop and closed-loop control device is configured to first close the supply valve and then to close the inlet valve; wherein the vaporizer unit is configured to vaporize the cryogen accommodated in the closed-off volume so as to subject the closed-off volume to a pressure which is higher than a pressure prevailing in the storage vessel; wherein the open-loop and closed-loop control device is configured to control the supply valve in such a way that the supply valve discharges the vaporized cryogen from the closed-off volume to the consumer when the consumer has a load requirement; and, wherein the open-loop and closed-loop control device is configured, when the supply valve is open, to open the inlet valve as soon as the pressure in the volume falls below the pressure prevailing in the storage vessel.

9. The conveying device according to claim 8, wherein the supply valve is arranged downstream from the inlet valve.

10. The conveying device according to claim 8, wherein the volume is provided between the inlet valve and the supply valve.

11. The conveying device according to claim 8, wherein the volume is formed by means of one or more pipe loops, a pipeline, and/or a storage volume.

Description

[0048] Further advantageous embodiments of the method and/or of the conveying device are the subject matter of the dependent claims and of the exemplary embodiments of the method and/or of the conveying device described below. Furthermore, the method and/or the conveying device are explained below in more detail with reference to the accompanying figures based upon preferred embodiments.

[0049] FIG. 1 shows a schematic view of an embodiment of a conveyor assembly for conveying hydrogen;

[0050] FIG. 2 shows a graph which schematically illustrates the functionality of the conveyor assembly according to FIG. 1; and

[0051] FIG. 3 shows a schematic block diagram of an embodiment of a method for supplying a consumer with a cryogen from a storage vessel.

[0052] In the figures, the same or functionally equivalent elements have been provided with the same reference signs unless otherwise indicated.

[0053] FIG. 1 shows a schematic view of an embodiment of a conveyor assembly 1 for conveying hydrogen H2 from a storage vessel 2 to a consumer 3. The conveyor assembly 1 is configured to supply the consumer 3 continuously with gaseous hydrogen H2 at a constant supply pressure of at most 6 bara, preferably from 1 to 2.5 bara, and at a temperature of approximately +10 to +25 C., independently of movements of the storage vessel 2. The conveyor assembly 1 can also be referred to as a hydrogen conveyor assembly. The storage vessel 2 and/or the consumer 3 can be part of the conveyor assembly 1.

[0054] The conveyor assembly 1 is particularly suitable for mobile applications. The conveyor assembly can preferably be part of a vehicle, in particular part of a land vehicle, of a watercraft or of an aircraft. For example, the conveyor assembly 1 is part of a ship such as a passenger ferry, a motor vehicle for example a truck or utility vehicle, or the like.

[0055] The storage vessel 2 can also be referred to as a storage tank. A plurality of storage vessels 2 can also be provided (not shown). The storage vessel 2 can be designed rotationally symmetrical with respect to a center axis or axis of symmetry 4. The axis of symmetry 4 can be oriented perpendicular to a direction of gravity g. This means that the storage vessel 2 is in a lying or horizontal position. However, the storage vessel 2 can also be positioned upright or vertically. In this case, the axis of symmetry 4 is oriented parallel to the direction of gravity g.

[0056] The storage vessel 2 is suitable for accommodating liquid hydrogen H2 (boiling point 1 bara: 20.268 K=252.882 C.). The storage vessel 2 can therefore also be referred to as a hydrogen storage vessel or as a hydrogen storage tank. However, the storage vessel 2 can also be used for other cryogenic liquids. Examples of cryogenic fluids or liquids, or cryogens for short, are liquid helium He in addition to the aforementioned liquid hydrogen H2 (boiling point 1 bara: 4.222 K=268.928 C.), liquid nitrogen N2 (boiling point 1 bara: 77.35 K=195.80 C.) or liquid oxygen O2 (boiling point 1 bara: 90.18 K=182.97 C.).

[0057] The liquid hydrogen H2 is accommodated in the storage vessel 2. As long as the hydrogen H2 is in the two-phase region, a gas zone 5 with vaporized hydrogen H2 and a liquid zone 6 with liquid hydrogen H2 can be provided in the storage vessel 2. After entering the storage vessel 2, the hydrogen H2 thus has two phases with different aggregate states, viz., liquid and gaseous. This means that, in the storage vessel 2, there is a phase boundary 7 between the liquid hydrogen H2 and the gaseous hydrogen H2. A pressure sensor 8, which can detect the pressure in the storage vessel 2, is associated with the storage vessel 2. The pressure in the storage vessel 2 is approximately 3.5 bara. The pressure in the storage vessel 2 is substantially constant.

[0058] A plurality of consumers 3 can be provided. However, only one consumer 3 is discussed below. The consumer 3 is preferably a fuel cell. In the present case, a fuel cell is understood to mean a galvanic cell that converts into electrical energy the chemical reaction energy of a continuously supplied fuel-in the present case, hydrogen H2and of an oxidantin the present case, oxygen. By means of the obtained electrical energy, an electric motor (not shown) can be driven, for example. For a stable operation of the consumer 3, it is necessary as mentioned above to supply the consumer 3 with gaseous hydrogen at a defined supply pressure.

[0059] In mobile applications, movements of the liquid hydrogen H2 accommodated in the storage vessel 2 must be expected. In the case of a horizontally-arranged, cylindrical storage vessel 2, a sloshing of the liquid hydrogen H2 over a large area is promoted by the mass inertia of the liquid hydrogen H2 and the curvature, present due to the horizontal installation, of the storage vessel 2, both against its cylindrical outer wall and against its ends.

[0060] This swashing, also known as sloshing, leads to cooling of the gas phase in the gas zone 5 above the liquid hydrogen H2 and thereby to pressure reduction of a gas cushion forming above the liquid hydrogen H2. Depending upon the movements of the storage vessel 2, this can have undesirable effects on the supply pressure available for operating components of the consumer 3, which can lead to an unstable operation of the consumer 3.

[0061] In order to provide the suitable supply pressure for the consumer 3, it is possible to use a liquid-cooled and liquid-stored pump for pumping liquid hydrogen. However, such a pump has moving parts. In addition, in the case of intermittent operation of the pump, bubbles can form in the liquid hydrogen H2 due to heating of said pump. This may lead to a malfunctioning of the pump. Alternatively, the hydrogen H2 can first be vaporized and then brought to the necessary supply pressure using a compressor. However, this is unfavorable in terms of energy use.

[0062] Furthermore, the storage vessel 2 can also be operated directly at the supply pressure. In this case, an equilibrium with the liquid phase and the gas phase layered thereabove is established in storage vessel 2. Due to the low surface tension of liquid hydrogen, a movement of the storage vessel 2, for example, when the latter is arranged in or on a vehicle as mentioned above, leads to the liquid phase and the gas phase being mixed with one another, and the liquid hydrogen H2 thereby cooling the warmer gaseous hydrogen H2. It is then not possible to maintain the supply pressure until an equilibrium is established between the temperature of the liquid hydrogen H2 and the gaseous hydrogen H2. These aforementioned problems must be solved with the aid of the conveyor assembly 1.

[0063] The conveyor assembly 1 has a conveying device 9. In contrast to the conveyor assembly 1, the storage vessel 2 and/or the consumer 3 are preferably not part of the conveying device 9. However, it is not ruled out that the storage vessel 2 and/or the consumer 3 are part of the conveying device 9.

[0064] The conveying device 9 comprises a line 10 which leads out from the storage vessel 2 below the phase boundary 7, i.e., in the region of the liquid zone 6. With the aid of the line 10, the liquid hydrogen H2 can be supplied from the storage vessel 2 to an inlet valve V2 of the conveying device 9. A vaporizer unit 11 is placed downstream from the inlet valve V2. The vaporizer unit 11 is suitable for vaporizing the liquid hydrogen H2 by introducing heat Q.

[0065] The inlet valve V2 is operatively connected via an operative connection 12 to an open-loop and closed-loop control device 13 of the conveying device 9. The operative connection 12 can be a data connection. The operative connection 12 can be wireless or wired. The open-loop and closed-loop control device 13 is suitable for opening and closing the inlet valve V2 as needed. The open-loop and closed-loop control device 13 can also be suitable for receiving and/or evaluating sensor signals from the pressure sensor 8.

[0066] A header 14 leads from the inlet valve V2 to a supply valve V1. The vaporizer unit 11 can be part of the header 14. The header 14 can be guided through the vaporizer unit 11. The vaporizer unit 11 can be connected to the header 14. A header is to be understood in particular as an enclosed volume which can be pressurized. In particular, a header is to be understood in the present case to mean a volume which is located between the valves V1, V2 and can be pressurized.

[0067] The header can also be referred to as a volume, pressure accumulator or collector. The terms header, volume, pressure accumulator or collector can accordingly be exchanged with one another as desired. The header 14 can be realized, for example, by a tube loop or a plurality of tube loops with, for example, a length of 15 to 20 m and a diameter of 200 to 250 mm. The pipe loop can run in a meandering manner. A pressure of 3 to 10 bara can prevail in the header 14.

[0068] The header 14 is also part of the conveyor device 9. A pressure sensor 15 for monitoring the pressure of the header 14 is connected to the header 14. The pressure sensor 15 is placed in the header 14 downstream from the vaporizer unit 11 and upstream from the supply valve V1. The terms downstream and upstream are to be understood with regard to a flow direction of the hydrogen H2 from the storage vessel 2 to the consumer 3. The pressure sensor 15 can communicate with the open-loop and closed-loop control device 13 in such a way that the open-loop and closed-loop control device 13 receives and/or evaluates sensor signals of the pressure sensor 15.

[0069] The supply valve V1 is coupled to the open-loop and closed-loop control device 13 via an operative connection 16. The operative connection 16 can be a data connection. The operative connection 16 can be wireless or wired. The open-loop and closed-loop control device 13 is suitable for opening and closing the supply valve V1 as needed.

[0070] A line 17 and a distributor 18 which distributes the gaseous hydrogen H2 to a plurality of consumers 3 are connected downstream from the supply valve V1. In the event that only one consumer 3 is provided, the distributor 18 can be omitted. A pressure of 1 to 2.5 bara, i.e., a suitable supply pressure for the consumer 3, prevails in the line 17 and/or in the distributor 18. The pressure in the header 14 is thus significantly higher compared to the pressure in the line 17 and/or the distributor 18.

[0071] The line 17 has a pressure sensor 19 which is coupled to the open-loop and closed-loop control device 13 via an operative connection 20. Furthermore, the line 17 comprises a flow sensor 21 which is coupled to the open-loop and closed-loop control device 13 via an operative connection 22. The open-loop and closed-loop control device 13 is configured to evaluate sensor signals from the pressure sensor 19 and/or from the flow sensor 21, and to receive them via the operative connections 20, 22.

[0072] The functionality of the conveyor assembly 1 or of the conveying device

[0073] 9 is explained below with reference to FIG. 2, which shows a graph in which a pressure p in the storage vessel 2 or in the header 14 and a load or load requirement L of the consumer 3 are plotted over the time t.

[0074] In FIG. 2, the time t in seconds is plotted on the right axis. The pressure p in the storage vessel 2 or in the header 14 is plotted in bar on the vertical axis, and the load requirement L of the consumer 3 is plotted in percent. A pressure p14 prevailing in the header 14 is shown by a solid line. A pressure p2 prevailing in the storage vessel 2, which is substantially constant, is illustrated with a dot-and-dash line. A dashed line 23 represents an opening and closing behavior of the supply valve V1. A double dot-dashed line 24 represents an opening and closing behavior of the inlet valve V2. The load requirement L of the consumer 3 is shown with a dotted line.

[0075] At a time to, both valves V1, V2 are completely open. As long as the consumer 3 has a load requirement L, the inlet valve V2 is open and the supply valve V1 controls the flow of gaseous hydrogen H2 to the consumer 3. This takes place on the basis of sensor data from the pressure sensor 19 and/or from the flow sensor 21 with the aid of the open-loop and closed-loop control device 13. The vaporizer unit 11 vaporizes the liquid hydrogen H2 from the storage vessel 2.

[0076] At a time t1, the load requirement L begins to be reduced. According to the decreasing load requirement L, the supply valve V1 is closed with a slight delay starting at a time t2. At a time t3, the load requirement L is zero percent. The supply valve V1 is completely closed with a slight delay at a time t4. At the time t3, the inlet valve V2 is still completely open. At the time t4, the inlet valve V2 is completely closed. Starting from the time t4, the consumer 3 is accordingly also no longer supplied with hydrogen H2. The consumer 3 is supplied with hydrogen H2 only in the event of a load requirement L.

[0077] The header 14 now forms a closed volume starting at the time t4. With the aid of the vaporizer unit 11, the header 14 can now be pressurized by vaporizing the liquid hydrogen H2 from the storage vessel 2. For this purpose, the vaporizer unit 11 introduces heat Q into the liquid hydrogen H2. The vaporization of the hydrogen H2 is indicated in the graph with the aid of a hatched region 25. At a time t5, the hydrogen H2 in the header 14 and in the vaporizer unit 11 is completely vaporized and, as mentioned above, a pressure of 3 to 10 bara prevails in the header 14.

[0078] The hatched region 25 represents in particular the pressure build-up by post-vaporization of the liquid hydrogen H2 still present in the vaporizer unit 11. In normal operation, the vaporizer unit 11 is not filled completely with gas, but in pipes of the vaporizer unit 11, a liquid is produced from the load and the heat transfer. This liquid level of the liquid hydrogen H2 is used for pressure build-up. At the time t5, all hydrogen H2 is vaporized in the vaporizer unit 11 and in the header 14.

[0079] At an arbitrary time t6 at which both valves V1, V2 are still closed, there is a load requirement L of the consumer 3. The supply valve V1 is opened with a slight delay at a time t7 and is controlled on the basis of sensor data from the pressure sensor 19 and from the flow sensor 21 via the open-loop and closed-loop control device 13 in such a way that the consumer 3 is supplied with gaseous hydrogen H2 with a suitable supply pressure as mentioned above. A rapid approach of the consumer 3 is possible by the hydrogen H2 stored in the header 14, as indicated in FIG. 2 with the aid of a hatched region 26.

[0080] Since a high pressure p14 now prevails in the header 14 at the time t6, it is possible to immediately supply the consumer 3 with gaseous hydrogen H2. It is then possible to dispense with first filling the vaporizer unit 11 and vaporizing the liquid hydrogen H2 under the load requirement L. At a time t8, the load requirement is 100 percent. The supply valve V1 is completely opened with a short delay at a time t9. The inlet valve V2 is still closed at the time t9.

[0081] At a time t10, the pressure in the header 14 falls below the pressure in the storage vessel 2. With a short delay, the inlet valve V2 can be opened again at a time t11 in order to charge the vaporizer unit 11 and/or the header 14 with liquid hydrogen H2 from the storage vessel 2. The consumer 3 can be supplied again with the suitable supply pressure via the supply valve V1.

[0082] FIG. 3 shows a schematic block diagram of an embodiment of a method for supplying the consumer 3 with hydrogen H2 from the storage vessel 2. The method is carried out with the aid of the conveyor assembly 1 or the conveying device 9.

[0083] In the method, in a step S1, a part of the hydrogen H2 from the storage vessel 2 is introduced into the header 14 that can be closed off from the consumer 3 and from the storage vessel 2. For this purpose, the inlet valve V2 is open. In a step S2, the header 14 is closed off from the consumer 3 and from the storage vessel 2. For this purpose, the supply valve V1 is closed during step S2. During step S2, the inlet valve V2 placed upstream from the supply valve V1 is also closed.

[0084] In a step S3, the hydrogen H2 is vaporized in the closed-off header 14 so as to subject the header 14 to the pressure p14 which is higher than the pressure p2 prevailing in the storage vessel 2. During the step S3, heat Q is introduced into the liquid hydrogen H2 in the header 14 with the aid of the vaporizer unit 11 in order to completely vaporize the liquid hydrogen H2 in the header 14.

[0085] In a step S4, in the event of a load requirement L of the consumer 3, the vaporized hydrogen H2 is discharged from the header 14 to the consumer 3. During step S4, the pressure p14 prevailing in the header 14 is reduced to the supply pressure suitable for the consumer 3 when the hydrogen H2 is discharged from the header 14 with the aid of the supply valve V1. The supply pressure suitable for the consumer 3 is smaller than the pressure p2 prevailing in the storage vessel 2.

[0086] During step S4, the supply valve V1 is opened in dependence on the load requirement L of the consumer 3. The supply valve V1 is controlled with the aid of the open-loop and closed-loop control device 13 on the basis of sensor signals from the pressure sensor 19 arranged downstream from the supply valve V1 and/or sensor signals of the flow sensor 21.

[0087] The inlet valve V2 remains closed as long as the pressure p14 in the header 14 is greater than the pressure p2 prevailing in the storage vessel. The inlet valve V2 is opened as soon as the pressure p14 in the header 14 drops below the pressure p2 prevailing in the storage vessel.

[0088] Although the present invention has been described with reference to exemplary embodiments, it can be modified in many ways within the scope of the claims.

REFERENCE SIGNS USED

[0089] 1 Conveyor assembly [0090] 2 Storage vessel [0091] 3 Consumer [0092] 4 Axis of symmetry [0093] 5 Gas zone [0094] 6 Liquid zone [0095] 7 Phase boundary [0096] 8 Pressure sensor [0097] 9 Conveying device [0098] 10 Line [0099] 11 Vaporizer unit [0100] 12 Operative connection [0101] 13 Open-loop and closed-loop control device [0102] 14 Header/volume [0103] 15 Pressure sensor [0104] 16 Operative connection [0105] 17 Line [0106] 18 Distributor [0107] 19 Pressure sensor [0108] 20 Operative connection [0109] 21 Flow sensor [0110] 22 Operative connection [0111] 23 Line [0112] 24 Line [0113] 25 Region [0114] 26 Region [0115] g Direction of gravity [0116] H2 Hydrogen/cryogen [0117] L Load requirement [0118] p Pressure [0119] p2 Pressure [0120] p14 Pressure [0121] Q Heat [0122] S1 Step [0123] S2 Step [0124] S3 Step [0125] S4 Step [0126] t Time [0127] t0 Time [0128] t1 Time [0129] t2 Time [0130] t3 Time [0131] t4 Time [0132] t5 Time [0133] t6 Time [0134] t7 Time [0135] t8 Time [0136] t9 Time [0137] t10 Time [0138] t11 Time [0139] V1 Supply valve [0140] V2 Inlet valve